Regular Expressions Cheat Sheet

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Anchors
Sample Patterns
^
Start of line +
([A-Za-z0-9-]+)
Letters, numbers and hyphens
\A
Start of string +
(\d{1,2}\/\d{1,2}\/\d{4})
Date (e.g. 21/3/2006)
$
End of line +
([^\s]+(?=\.(jpg|gif|png))\.\2)
jpg, gif or png image
\Z
End of string +
(^[1-9]{1}$|^[1-4]{1}[0-9]{1}$|^50$)
Any number from 1 to 50 inclusive
\b
Word boundary +
(#?([A-Fa-f0-9]){3}(([A-Fa-f0-9]){3})?)
Valid hexadecimal colour code
\B
Not word boundary +
((?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,15})
8 to 15 character string with at least one
\<
Start of word
\>
End of word
Character Classes
upper case letter, one lower case letter,
and one digit (useful for passwords).
(\[email protected][a-zA-Z_]+?\.[a-zA-Z]{2,6})
Email addresses
(\<(/?[^\>]+)\>)
HTML Tags
\c
Control character
\s
White space
\S
Not white space
\d
Digit
\D
Not digit
\w
Word
*
0 or more +
\W
Not word
*?
0 or more, ungreedy +
\xhh
Hexadecimal character hh
+
1 or more +
(a|b)
a or b +
\Oxxx
Octal character xxx
+?
1 or more, ungreedy +
(...)
Group +
?
0 or 1 +
(?:...)
Passive Group +
??
0 or 1, ungreedy +
[abc]
Range (a or b or c) +
{3}
Exactly 3 +
[^abc]
Not a or b or c +
POSIX Character Classes
Note
These patterns are intended for reference purposes and have not been extensively tested.
Please use with caution and test thoroughly before use.
Quantifiers
Ranges
.
Any character except
new line (\n) +
[:upper:]
Upper case letters
{3,}
3 or more +
[a-q]
Letter between a and q +
[:lower:]
Lower case letters
{3,5}
3, 4 or 5 +
[A-Q]
Upper case letter +
[:alpha:]
All letters
{3,5}?
3, 4 or 5, ungreedy +
[:alnum:]
Digits and letters
[0-7]
Digit between 0 and 7 +
[:digit:]
Digits
\n
nth group/subpattern +
[:xdigit:]
Hexadecimal digits
[:punct:]
Punctuation
\
Escape Character +
[:blank:]
Space and tab
\n
New line +
[:space:]
Blank characters
\r
Carriage return +
[:cntrl:]
Control characters
\t
Tab +
[:graph:]
Printed characters
\v
Vertical tab +
[:print:]
Printed characters and
\f
Form feed +
g
Global match
spaces
\a
Alarm
i
Case-insensitive
Digits, letters and
[\b]
Backspace
m
Multiple lines
underscore
\e
Escape
s
Treat string as single line
\N{name}
Named Character
x
Allow comments and
[:word:]
Special Characters
between A and Q +
Note
Ranges are inclusive.
Pattern Modifiers
white space in pattern
Assertions
String Replacement (Backreferences)
e
Evaluate replacement
U
Ungreedy pattern
?=
Lookahead assertion +
?!
Negative lookahead +
$n
nth non-passive group
?<=
Lookbehind assertion +
$2
"xyz" in /^(abc(xyz))$/
?!= or ?<!
Negative lookbehind +
$1
"xyz" in /^(?:abc)(xyz)$/
?>
Once-only Subexpression
$`
Before matched string
^
[
.
?()
Condition [if then]
$'
After matched string
$
{
*
?()|
Condition [if then else]
$+
Last matched string
(
\
+
?#
Comment
$&
Entire matched string
)
|
?
$_
Entire input string
<
>
$$
Literal "$"
Note
Items marked + should work in most
regular expression implementations.
Metacharacters (must be escaped)
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